1. Field of the Invention
The invention concerns a drill head for the attachment of bone drills or bone milling cutters, as well as the bone drills or milling cutters themselves, especially for preparing bone cavities into which enossal prosthetic elements can be inserted. The designation "bone drill" or "bone milling cutter" is meant to include all drills or cutters with which, in the field of human or veterinary medicine, including the dental field, material can be removed from teeth, bones and bone-like tissue, as well as from corresponding substitute materials. Finally the invention concerns also dental and half-implants, being particularly simply inserted with these instruments.
2. Prior Art
Very accurate working is essential when making bone cavities for the insertion of enossal prosthetic elements so that the bone cavities exhibit the desired dimensions and the essential alignment. This applies in particular in the case of bone cavities designed for the insertion of dental implants. Additional problems arise here occassioned by the small extension of the jawbone, the teeth still remaining in it and the scant working space available.
Until now the production of large and exactly-shaped bone cavities has been effected by free-hand using conventional drills and bone cutters normal in the field of dental medicine and surgery, these being mounted individually on corresponding drill heads. It is extremely difficult and time-consuming to create the desired bone cavities with these tools, and despite the use of markers, molds and templates one does not always succeed in achieving the necessary accuracy.
A considerable proportion of the failures with enossal implants can be attributed to the previously-mentioned difficulties. When for example the bone cavity is wider just in certain areas than the implant to be inserted, the danger of an infection between implant and bone wall is increased. In addition gum tissue invagination ensues in these areas, so preventing the bone tissue from growing together with the implant.
There is no known bone drill with which one can make deep, exactly-shaped bone cavities suitable for the insertion of implants in one operation. It is not even possible to make simple and exactly-shaped cylindrical holes in bones using the known drills, since the cutting heads are very short and shift during the drilling operation. There are as yet no long drills where shifting is prevented. This could be attributable to the fact that it is difficult to so eliminate the heat resulting during drilling or cutting that temperatures of 50.degree. C. to 52.degree. C., at which coagulation of the protein tissue occurs, are not exceeded. Cooling of the drilling region and of the drill with a cooling medium also becomes difficult with increasingly long drills.
The following publications Nos. are quoted as prior art: DT-PS 360382 DT-PS 445682 DT-PS 711634 DT-PS 1255857 DT-AS 1018583 DT-OS 2331023 DT-OS 2419080 DT-OS 2543723 DT-GM 6803765 DT-GM 7215122 DT-GM 7322725.
The following are in addition mentioned:
The use of common drill heads with corresponding special speed reductions and with small tolerances in the mounting, to guarantee a central passage of the cutter and a transfer of high pulling power to it. The use of fast-moving turbocutters, eg. the "Lindemann Cutter", for preparing the slots for laminar implants.
There are as yet no instruments enabling a simple, quick and accurate preparation of bone cavities.